Cruise Control Problem
 

I have a 98 Boxster with a non-operational cruise control.

The button to turn the cruise control on works - and turns on the cruise control light on the dashboard, but the cruise control "set" toggle doesn't trigger the cruise control. On cancel, I can see the cruise control light on the dashboard blink. Any ideas on how I can figure out the root cause of the problem?

I would suggest replacing the clutch switch. I had the same issue when I purchased mine and that solved the problem. It not too hard to do.

+1 on this. It is either the clutch or brake switch. They are known to fail.

Before you do anything else, find the clutch switch and pull out on the plunger piece that is pushed by the clutch pedal. It is adjustable and it simply may be pushed too far in to be actuated by the clutch pedal when you release it.